1. Field of the Invention
The present invention relates to the structure of a semiconductor light emitting element and an array structure of the light emitting elements.
2. Description of the Related Art
A semiconductor light emitting element array is composed of an assembly of a plurality of LDs (Laser Diodes) or LEDs (Light Emitting Diodes) and used as an optical source for a writing head of a laser printer, for instance.
A typical monolithic structure of the semiconductor light emitting element is disclosed in Japanese Laid Open Patent Application (KOKAI) Nos. 60-90784, 60-99673 and 60-116479.
The array structure disclosed in the above-mentioned patent documents comprises a pair of electrodes for applying an electric voltage which are arranged in such a way that one of the electrodes is disposed on an upper surface of a substrate and the other is disposed on a lower surface of the substrate.
Such a structure does not have any significant problems in the event that the lower side electrode is used as a common counter electrode for all of the selective electrodes which are formed on the upper surface of the substrate separately from each other.
However, in the event that the lower electrode is to be divided to a plurality of counter electrodes for upper side electrodes, the lower counter electrodes have to be patterned strictly corresponding to the upper electrodes. Patterning the lower electrodes corresponding to the upper electrodes requires a high and troublesome techniques of a double-exposure patterning process, which limits the pattern density of the lower electrodes and also restricts the optical elements which can be combined with the array structure.